The biggest cause of overpopulation is ___________ people are having lots of children.
A. but B. because C. and D. enough
11. Many people _________ big families in Pakistan.
A. has B. having C. have D. to have
12. To help the community, students can __________ their schools and the streets.
A. clean B. recycling C. cleaning D. recycle
13. _____________ is the average age that people live to.
A. Life expectancy B. Pollution C. Overpopulation D. Death rate
14. We need people ____________ pictures.
A. painting B. to paint C. to painting D. painted